Publication Summary

Mercury levels were assessed in 60 fish for the first year of long-term monitoring of mercury in fish tissues across Washington State. Previous Department of Ecology studies identified elevated mercury levels which led to fish consumption advisories.

This 2005 study found mercury levels to be within typical ranges (0 - 300 ppb) of previous fish tissue studies conducted within the state. Less than 10% of samples were above the EPA recommended criterion for mercury (300 ppb), and no samples were above the National Toxics Rule criterion for mercury (825 ppb).

Concerns about mercury in our environment have increased due to the persistent, bioaccumulative, and toxic nature of this substance. To address these concerns, a Mercury Chemical Action Plan was developed in 2003 by the Washington State Departments of Ecology and Health with assistance from an advisory committee representing business, health, environmental, and local government organizations.

The Mercury Chemical Action Plan identified the need for improved understanding of mercury′s behavior in the environment in order to guide management of this environmental toxicant. The 2005 State Legislature provided funds to begin long-term monitoring of mercury in the freshwater environments of Washington. This document presents results from the first year of a long-term monitoring effort for mercury in fish tissue.

The primary goal of this project is to monitor mercury levels in edible tissue from freshwater fish at six sites per year for five years (30 sites total) to characterize temporal trends in fish tissue mercury levels.

During 2005, largemouth and smallmouth bass were collected from six sites in Washington: Liberty Lake, Long Lake (Spokane River), Loon Lake, Potholes Reservoir, Silver Lake, and the Yakima River.

Mercury concentrations in edible tissues ranged from 17 to 372 parts per billion (ppb). Fish ages and total lengths ranged from 1-12 years and 247-508 millimeters, respectively. Higher concentrations of mercury were found in the older and larger fish. Five of the 60 fish collected contained mercury levels higher than the EPA′s Recommended Fish Tissue Criterion of 300 ppb. No fish had mercury levels higher than the National Toxics Rule Criterion of 825 ppb.

Water chemistry and sediment mercury levels will be measured in subsequent years of the study to help understand patterns in fish tissue mercury levels over space and time.

Link to EIM data for User Study ID HgFish05